When did teams start high 5'ing each other instead of shaking hands with the other team? I know the answer is, "a while" or, "as long as I remember" but it still bugs me. Anyone have any idea when this started?

First team I can remember doing this is the Yankees doing fist bumps in the late 90s. It seemed to start with Posada taking his mask off, fist bumping the pitcher, and then those two going around to everybody else.